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1964 Corvair EM-EV
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Discussion Starter #1 (Edited)
Greetings all.

I am new to the forum and thought I would share my project. I have been looking around for Corvair conversions, but it seems few are complete. I completed mine in July 2020 and I can tell all of you first hand, it is totally awesome. I never had the nerve to drive the car terribly far, or terribly fast especially with my family riding along. Old cars are just not as safe. So, since I always use it for short, local trips, and I love to tinker and engineer stuff, it seemed a perfect candidate. No longer do I have to start the car, let it run the gasoline intensive warm up routine for a few minutes, just to complete a 10-15 minute drive.

I added an under dash heater box to keep the window fog down. I installed seat heaters to keep us warmer. Its now a 3 season car, for the most part. I would say my heating system works as well as the stock system, at least. I completely changed the weight distribution of the car. It is now nearly 50/50. This means it handles much more like a typical car, but i gave up the super light steering. It also means the brakes need some pretty big modifications. The weight distribution during braking is now very front heavy, so care has to be taken to keep the rear wheels from locking up. The springs and dampers also had to be changed. I went with the SBC springs from Clarks in the front and springs from a 63 that I cut for the rear (I removed the leaf spring). I have yet to do any super dramatic driving to see how it understeers now. I will likely do that on a rainy day first.

I installed a 120hp Hyper 9 AC motor in the back. Its coupled to a 3:55 diff and a 3spd that I leave in 2nd gear (all the time, I don't shift). It means its not a rocket off the line, but very fun from 10-50mph and has a top speed of 77mph. All totally acceptable for me.

I used 7 salvaged battery modules form a 2012 tesla model S that was in an accident. I feel good about this, since I used something already manufactured and didn't demand more resources from the earth. LiPo batteries are very resource intensive to manufacture. But... so is aluminum and folks seem ok with that. I calculate a range of 120miles. I only charge them to 85% to extend their life, so I would guess I get 90 miles at most on a charge. That is a week of going to work for me. I don't know the range just yet because my odometer has never worked and I haven't taken the time to figure it out yet. We had been just having so much fun this summer and fall, it hasn't been a priority.

I used a Orion2 BMS and a 2,5kW charger. I would not recommend using any LiPo batteries without a battery management system. LiPos are great for energy density (especially the tesla modules) but they are finicky and can be dangerous if not managed well.

Here are some pics. I hope this inspires some folks to give it a try. It was a fun challenge and very rewarding (though expensive). Also... I rebuilt my differential during the project. Now I can officially say, the car leaks more oil as a EV than it did running on gas. I guess that will be a project for another day.
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Great choice. Love the Corvairs. Nice job as well.

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Nice job! :)

I completely changed the weight distribution of the car. It is now nearly 50/50. This means it handles much more like a typical car, but i gave up the super light steering. It also means the brakes need some pretty big modifications. The weight distribution during braking is now very front heavy, so care has to be taken to keep the rear wheels from locking up. The springs and dampers also had to be changed. I went with the SBC springs from Clarks in the front and springs from a 63 that I cut for the rear (I removed the leaf spring). I have yet to do any super dramatic driving to see how it understeers now. I will likely do that on a rainy day first.
Did you consider placing a couple of the modules over the motor for a more suitable weight distribution?

The leaf spring was added in 1964 to improve the behaviour of the swing-axle suspension. It would probably handle better with softer coil springs and the leaf (or "camber compensator") replaced.

I installed a 120hp Hyper 9 AC motor in the back. Its coupled to a 3:55 diff and a 3spd that I leave in 2nd gear (all the time, I don't shift). It means its not a rocket off the line, but very fun from 10-50mph and has a top speed of 77mph. All totally acceptable for me.
That makes sense. Have you tried starting off in first gear for better low-speed acceleration?

I used 7 salvaged battery modules form a 2012 tesla model S that was in an accident. I feel good about this, since I used something already manufactured and didn't demand more resources from the earth. LiPo batteries are very resource intensive to manufacture. But... so is aluminum and folks seem ok with that.
...

I used a Orion2 BMS and a 2,5kW charger. I would not recommend using any LiPo batteries without a battery management system. LiPos are great for energy density (especially the tesla modules) but they are finicky and can be dangerous if not managed well.
Tesla cells are not LiPo (lithium polymer), but yes, a BMS is a good idea, especially with Tesla's cell chemistry.
 

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1964 Corvair EM-EV
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Discussion Starter #4
Nice job! :)
Thanks very much! It was a very fun project. I would consider it rather simple, compared to the awesome stuff I see on this forum.
Did you consider placing a couple of the modules over the motor for a more suitable weight distribution?
I didn't consider distributing the modules after doing my new weight distribution calculations. I wanted to get rid of the bias towards the rear wheels, frankly. It was my understand that the primary purpose of the transverse leaf spring was to allow for softer coils, reducing the rear roll stiffness and the tendency to oversteer. I wasn't aware of any structural-like impact to the camber, from the leaf spring. It seems the reduced roll stiffness would keep the car form climbing up over that outside swingarm. I suppose that is a way of compensating for that negative camber under load. With the new weight in the front, I suspect the car will understeer nicely, especially with the stiffer front ARB on the 64's. I also wanted to keep the modules together for easier wiring, and now I have room for some groceries in the trunk!

Plus, relocating two modules would have reduced the weight up front enough that the SBC springs from Clarks would have been too stiff, and Clarks mid engine conversion springs would have been too soft. I would have been in custom spring territory then, and I wasn't up for that.

That makes sense. Have you tried starting off in first gear for better low-speed acceleration?
I have not. The car was an automatic originally, so i don't have the linkage and such to shift anyway. I might climb under there one day, shift it by hand, just to see how it feels. I originally planned to use the 2spd powerglide that came in the car, but I couldn't figure out a graceful way to run the engagement pump when the car wasn't moving and I really didnt want to use the torque converter or idle the electric motor. And when I took apart the powerglide to investigate, it was clear there was no way I was getting it back together! But i was able to take advantage of the auto shift lever to command direction. I added a two hall effect sensors to the original lever, so "D" and "R" do what you expect. I also added a third sensor to initiate regen on neutral in the "L" position for some engine braking on hills.

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Tesla cells are not LiPo (lithium polymer), but yes, a BMS is a good idea, especially with Tesla's cell chemistry.
Yes, thank you. You are totally right.
 

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1964 Corvair EM-EV
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Discussion Starter #5
Great choice. Love the Corvairs. Nice job as well.

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Thanks much! I have always loved Corvairs. I think they were so innovative, and growing up in Detroit, I'v always had a soft spot for them... especially the early models.
 

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I didn't consider distributing the modules after doing my new weight distribution calculations. I wanted to get rid of the bias towards the rear wheels, frankly.
I get that, but that's a Corvair... it's rear-heavy. If you change that, you have a significant job of re-tuning the suspenion to do.

It was my understand that the primary purpose of the transverse leaf spring was to allow for softer coils, reducing the rear roll stiffness and the tendency to oversteer. I wasn't aware of any structural-like impact to the camber, from the leaf spring. It seems the reduced roll stiffness would keep the car form climbing up over that outside swingarm. I suppose that is a way of compensating for that negative camber under load.
Close... the transverse leaf spring is there to add collective spring stiffness, to keep the swing-axle suspension from moving too much vertically, without adding excessive roll stiffness the way stiff coil springs at each wheel would. "Climbing up over that outside swingarm" is jacking, an inherent characteristic of the suspension geometry (which hasn't been changed, and isn't changed by springs or camber compensators) - it is the result of lateral force by the rear tires, regardless of the roll stiffness. It is bad mostly because of the resulting camber, but the raising of the rear end is also bad. You reduce jacking by stiffening the vertical motion (which is what the leaf spring does), not by reducing the roll stiffness.

Plus, relocating two modules would have reduced the weight up front enough that the SBC springs from Clarks would have been too stiff, and Clarks mid engine conversion springs would have been too soft. I would have been in custom spring territory then, and I wasn't up for that.
This is what I was saying about the consequences of changing the weight distribution - it means that you need a spring combination which no one offers (although you might be able to assemble it with some combination of front and rear springs intended for other configurations) because Corvairs don't have that distribution.

An alternative for almost any car to custom springs that fit the stock suspension, is coil-over shocks with adjustable spring perches... but they're not cheap.
 

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I have not. The car was an automatic originally, so i don't have the linkage and such to shift anyway.
Since it started as an automatic without a console shifter, not putting in a manual shifter is certainly understandable. It just seems like a missed opportunity to me to carry around the weight and bulk and complexity of a multi-speed transmission to use only one ratio... but that's relatively common in conversions.

I originally planned to use the 2spd powerglide that came in the car, but I couldn't figure out a graceful way to run the engagement pump when the car wasn't moving and I really didnt want to use the torque converter or idle the electric motor. And when I took apart the powerglide to investigate, it was clear there was no way I was getting it back together!
I think you dodged a bullet there - a lot of people have adapted Power Glides for EV conversions, but it's expensive and I can't see it as worthwhile in this century. Idling an electric motor to drive through a torque converter is certainly a terrible idea (now).

But i was able to take advantage of the auto shift lever to command direction. I added a two hall effect sensors to the original lever, so "D" and "R" do what you expect. I also added a third sensor to initiate regen on neutral in the "L" position for some engine braking on hills.

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Cool shifter, and nicely adapted for the conversion. :)

I had never seen the auto shifter of a Corvair before another current project (Planning to convert a 1968 Corvair 500). The first and second generation shifters are different, but both seem well-suited to this sort of adaptation.
 

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1964 Corvair EM-EV
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Discussion Starter #8
I get that, but that's a Corvair... it's rear-heavy. If you change that, you have a significant job of re-tuning the suspenion to do.


Close... the transverse leaf spring is there to add collective spring stiffness, to keep the swing-axle suspension from moving too much vertically, without adding excessive roll stiffness the way stiff coil springs at each wheel would. "Climbing up over that outside swingarm" is jacking, an inherent characteristic of the suspension geometry (which hasn't been changed, and isn't changed by springs or camber compensators) - it is the result of lateral force by the rear tires, regardless of the roll stiffness. It is bad mostly because of the resulting camber, but the raising of the rear end is also bad. You reduce jacking by stiffening the vertical motion (which is what the leaf spring does), not by reducing the roll stiffness.
Hmmm... by that logic, it seems i am in even better shape then. If a stiffer vertical spring rate helps reduce jacking, and reducing jacking helps with camber, and therefore oversteer, then my conversion is way less prone to oversteer. The cut springs from a 63 provides a vertical spring rate that is higher than stock.

Speaking of stock, the vertical spring rate for the 64s is nearly the same for the earlier years...its gotta be... same load and geometry and ride height and quality. Its the roll stiffness that was updated with the leaf spring. And they added a bigger ARB in the front. Both work together to reduce the oversteer, from what I understand. Less for Nader to complain about.

This is what I was saying about the consequences of changing the weight distribution - it means that you need a spring combination which no one offers (although you might be able to assemble it with some combination of front and rear springs intended for other configurations) because Corvairs don't have that distribution.

An alternative for almost any car to custom springs that fit the stock suspension, is coil-over shocks with adjustable spring perches... but they're not cheap.
Yep, you got it. Thats exactly the reason i wanted all the batteries in the front, so I could stay with springs already sized for the front end loads of conversions folks have done in the past. It sounds like you must own a Corvair, based on the posts. Adapting coil-overs in the front suspension in these cars is not worth the effort when Clarks sells springs and dampers sized for the front end load I added.

A equally difficult part of this conversion was updating the brake distribution. I ended up with a dual master cylinder update, a disc conversion in the front and added a brake proportioning valve. All of this helped increase the braking capacity of the car, and keeps the rear tires from locking up under severe braking. I did have to test a bunch since the braking regen contributes only to the rears. It took me a bit to get a regen curve that was agreeable.
 

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Hmmm... by that logic, it seems i am in even better shape then. If a stiffer vertical spring rate helps reduce jacking, and reducing jacking helps with camber, and therefore oversteer, then my conversion is way less prone to oversteer. The cut springs from a 63 provides a vertical spring rate that is higher than stock.
No, it's the opposite. The stiff springs mean a high roll stiffness, and a relatively high rear roll stiffness (versus the front) that the rear does more of the lateral load transfer, reducing rear traction and increasing the tendency to rear roll stiffness. The point of the leaf spring was to get a high spring rate for both sides moving together (to reduce oversteer) without causing a high roll stiffness (which would increase oversteer).

Speaking of stock, the vertical spring rate for the 64s is nearly the same for the earlier years...its gotta be... same load and geometry and ride height and quality. Its the roll stiffness that was updated with the leaf spring.
No, that's not how it works. The leaf spring adds to the vertical spring rate, so the coils could be (but were not necessarily) softer. The ride height depends on both stiffness and free length of the coils, and stiffness and initial curvature of the leaf. The leaf is relatively free to pivot in the middle (it's held by a single rubber pad) so it adds very little to roll stiffness. This is a "camber compensator", the opposite of a stabilizer or anti-roll bar.

The aftermarket camber compensator which was offered (by EMPI) before a similar device became stock for model year 1964 apparently didn't come with a change of springs, suggesting that it was set up with no preload (under no stress when sitting static), so it would not affect ride height. It would have little effect in one-wheel bumps so ride would not be noticeably changed, but when both rear wheels hit a bump at the same time it would be stiffer and that should be noticeable... if one were to test carefully enough. Reportedly the 1964 factory coils are softer to go with the addition of the factory leaf spring (which takes some of the load), so it could not only be at the same ride height, but ride the same over both-wheel bumps and better over single-wheel bumps (compared to 1963).

And they added a bigger ARB in the front. Both work together to reduce the oversteer, from what I understand. Less for Nader to complain about.
Yes, the stiffer front stabilizer or anti-roll bar increases the front's share of the lateral load transfer, increasing the tendency to understeer (or reducing oversteer).

It sounds like you must own a Corvair, based on the posts.
No, just an automotive technology enthusiast. :)

A equally difficult part of this conversion was updating the brake distribution. I ended up with a dual master cylinder update, a disc conversion in the front and added a brake proportioning valve. All of this helped increase the braking capacity of the car, and keeps the rear tires from locking up under severe braking. I did have to test a bunch since the braking regen contributes only to the rears. It took me a bit to get a regen curve that was agreeable.
That's another reason to keep something close to the original weight distribution - no need to change brake balance them. Of course, this wasn't a finely tuned performance machine to start with ;), so an overall brake upgrade is desirable.
 

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Discussion Starter #10
No, it's the opposite. The stiff springs mean a high roll stiffness, and a relatively high rear roll stiffness (versus the front) that the rear does more of the lateral load transfer, reducing rear traction and increasing the tendency to rear roll stiffness. The point of the leaf spring was to get a high spring rate for both sides moving together (to reduce oversteer) without causing a high roll stiffness (which would increase oversteer).
That's what I hoped you'd say. Your comment about jacking vs vertical spring rate suggested that you thought adding stiffness in the back would help oversteer.

No, that's not how it works. The leaf spring adds to the vertical spring rate, so the coils could be (but were not necessarily) softer. The ride height depends on both stiffness and free length of the coils, and stiffness and initial curvature of the leaf. The leaf is relatively free to pivot in the middle (it's held by a single rubber pad) so it adds very little to roll stiffness. This is a "camber compensator", the opposite of a stabilizer or anti-roll bar.
We are saying the same thing. The leaf spring addressed roll stiffness. It adds spring rate without adding much roll stiffness. This is the primary purpose of the spring and helped reduce oversteer in 64s. Its secondary purpose to help control the swing arm or the unloaded tire. If you ever watch the suspension move on a corvair, you will see that even with the leaf spring, the camber for the rear wheel is all over the place during compression and rebound. It does not help much, if at all.

The aftermarket camber compensator which was offered (by EMPI) before a similar device became stock for model year 1964 apparently didn't come with a change of springs, suggesting that it was set up with no preload (under no stress when sitting static), so it would not affect ride height. It would have little effect in one-wheel bumps so ride would not be noticeably changed, but when both rear wheels hit a bump at the same time it would be stiffer and that should be noticeable... if one were to test carefully enough. Reportedly the 1964 factory coils are softer to go with the addition of the factory leaf spring (which takes some of the load), so it could not only be at the same ride height, but ride the same over both-wheel bumps and better over single-wheel bumps (compared to 1963).
Yes, I can assure you that the 64 springs are alot softer. I can also assure you the ride height in the 64 is the same as the 63. The leaf spring added alot spring rate to the rear end. The symmetric loading of the rear end of the 64s is not noticeably different than the 63s. The asymmetric loading is noticeably different, as you describe as one-wheel bumps. This maintains the ride quality of the earlier models, makes the system less sensitive to tire pressure mistakes, and still helps address oversteer. Its a clever solution.

The EMP camber compensators for bugs and spitfires are actually more like "reverse leaf springs". They try to control the unloaded tire, and dont add much, if any, vertical spring stiffness by design. They have a different intention than the leaf spring on the Corvair.

One of the biggest issues with the Corvair is the combination of the swing arm rear suspension design with the traditional front end suspension design US auto designers were using at the time. The roll center for the front end was feet below the surface of the road. This helped produce a great turn in response, and helped make the huge cars feel agile, but it also caused a dramatic weight shift during turn in, which really loaded up the rear end. The combo made for a very tricky car to maneuver dramatically without oversteer.


That's another reason to keep something close to the original weight distribution - no need to change brake balance them. Of course, this wasn't a finely tuned performance machine to start with ;), so an overall brake upgrade is desirable.
Anyone consider converting a Corvair can overcome the challenges of a different weight distribution, if they so desire. They had tricky handling from the factory, and changing the distribution will help make it handle like a more traditional grocery getter. Since the car is well supported with aftermarket parts, (it has been used for front engine conversions, mid engine conversions and the front end sub-assemblies get used in hot rods), there are lots of options to manage the required changes in springs and dampers. In addition, there are lots of brake upgrade options and kits and the like. Maintaining the same weight distribution would make it simpler to convert, but it wouldn't help address the crappy handling. For folks interested in the free body diagram, and static force calculations, I am happy to share. In the end, my corvair ended up about 43lbs heavier than stock and went from a 38/62% front/rear distribution to 50/50%. The side effects of that are listed above, but since the car is so well supported with aftermarket stuff, and the factory handling could use updating, it was worth it to me.
 

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We are saying the same thing. The leaf spring addressed roll stiffness. It adds spring rate without adding much roll stiffness. This is the primary purpose of the spring and helped reduce oversteer in 64s. Its secondary purpose to help control the swing arm or the unloaded tire. If you ever watch the suspension move on a corvair, you will see that even with the leaf spring, the camber for the rear wheel is all over the place during compression and rebound. It does not help much, if at all.
The leaf spring doesn't change the geometry, so yes, the camber does exactly the same thing with the same wheel travel with or without the leaf. The point of the leaf is to reduce wheel travel due to the rear end rising, and that's how it helps camber.

Yes, I can assure you that the 64 springs are alot softer. I can also assure you the ride height in the 64 is the same as the 63. The leaf spring added alot spring rate to the rear end. The symmetric loading of the rear end of the 64s is not noticeably different than the 63s. The asymmetric loading is noticeably different, as you describe as one-wheel bumps. This maintains the ride quality of the earlier models, makes the system less sensitive to tire pressure mistakes, and still helps address oversteer. Its a clever solution.
Good. This is what I expected. It is clever, and has been used on swing-axle suspensions for a very long time. My wife's Triumph Spitfire has essentially the same solution, implemented years after the 1964 Corvair.

The EMP camber compensators for bugs and spitfires are actually more like "reverse leaf springs". They try to control the unloaded tire, and dont add much, if any, vertical spring stiffness by design. They have a different intention than the leaf spring on the Corvair.
But they do add vertical spring stiffness - that's all they do. They don't have preload, so at normal ride height they don't support any of the load. They have part of the functionality of the OEM leaf spring.

While there may have been add-ons for early Spitfires, the car always had a transverse leaf spring (at the rear). Originally the spring was rigidly clamped at the middle, so it acted as two independent cantilever springs, one for each side, effectively the same as coils. Starting with the Mark IV, only the bottom leaf of the pack was clamped so the rest could rock side-to-side - just like the 1964 Corvair's leaf - so it provided a high stiffness in symmetric wheel travel and relatively low roll stiffness... just like the 1964 Corvair's combination of coils and pivoting leaf.

One of the biggest issues with the Corvair is the combination of the swing arm rear suspension design with the traditional front end suspension design US auto designers were using at the time. The roll center for the front end was feet below the surface of the road. This helped produce a great turn in response, and helped make the huge cars feel agile, but it also caused a dramatic weight shift during turn in, which really loaded up the rear end. The combo made for a very tricky car to maneuver dramatically without oversteer.
I agree that a poor combination of front and rear roll centre heights is likely a substantial part of the problem. On the other hand, while a roll centre below the road surface is physically possible, it is unlikely; when it does occur in a competently designed suspension, it is millimetres rather than inches, let alone feet. The lower control arms body pivots would need to be far below the lower control arm ball joint - placing the arm pointing downward from hub to car - and the upper arm would need to at least as steep. Upper arms are routinely sloped this way, but not lower arms in a car that hasn't been ruined by someone who doesn't know what they're doing, such as by lowering radically with only a spring change.

I found a post in another forum which promised a list of many examples of actual roll centre heights, and I delayed this response until I could see the list, but that forum seems to be inactive I have not been able to complete registration to get access. I'm sure that if I can ever get to it, it will show that roll centre height is rarely negative and never "feet below the surface of the road".

But yes, a roll centre axis which is sloped very much downward toward the front makes the rear do more load transfer than the front until the vehicle rolls enough to move the springs and stabilizer bars, so it makes the car more responsive... and more prone to oversteer if the driver thrashes the steering wheel around.

The classic aircooled VW chassis with swing axles has a trailing arm front suspension with the front roll centre at ground level. Most front suspensions have a higher roll centre, so almost any random front suspension would safer with swing axles than the one in a Beetle. And yet most Beetles wore out or rusted out, rather than crashing in oversteer.

Anyone consider converting a Corvair can overcome the challenges of a different weight distribution, if they so desire. They had tricky handling from the factory, and changing the distribution will help make it handle like a more traditional grocery getter. Since the car is well supported with aftermarket parts, (it has been used for front engine conversions, mid engine conversions and the front end sub-assemblies get used in hot rods), there are lots of options to manage the required changes in springs and dampers. In addition, there are lots of brake upgrade options and kits and the like. Maintaining the same weight distribution would make it simpler to convert, but it wouldn't help address the crappy handling. For folks interested in the free body diagram, and static force calculations, I am happy to share. In the end, my corvair ended up about 43lbs heavier than stock and went from a 38/62% front/rear distribution to 50/50%. The side effects of that are listed above, but since the car is so well supported with aftermarket stuff, and the factory handling could use updating, it was worth it to me.
I really don't understand the point of a front-engine conversion of a Corvair. Yes, it would provide an independent rear suspension, but pre-1965 it's not a good suspension and even post-1965 it would be easier to start with a beam axle car and swap in IRS (in the 1970's it might be from a Corvette, Jag, whatever) than to start with the only Chevrolet car ever built with the engine not in the front and then put an engine in the front. The easiest way to get a front-engine Corvair is just to buy the one that GM made: the 1961-1963 Pontiac Tempest... although I suppose those are rare.

Of course in this electric conversion engine location and the resulting need for a transmission tunnel isn't an issue, and making the car resemble a front-engine design makes more sense.

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I'm not trying to promote a specific suspension design, but rather to explain why I think it makes sense to retain the feature that GM added to the Corvair's rear suspension to make it better, rather than reverting to the inferior previous version.
 
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